Thank God for multitasking. Can you imagine how dull life would be if we humans lacked the ability to rapidly and seamlessly shift our focus from one task or topic to another? We wouldn’t be able to listen to the radio while driving, have conversations while cooking, juggle assignments at work, or even chew gum while walking. The world would grind to a depressing halt.

The ability to multitask is one of the essential strengths of our infinitely amazing brains. We wouldn’t want to lose it. But as neurobiologists and psychologists have shown, and as Maggie Jackson has carefully documented, we pay a price when we multitask. Because the depth of our attention governs the depth of our thought and our memory, when we multitask we sacrifice understanding and learning. We do more but know less. And the more tasks we juggle and the more quickly we switch between them, the higher the cognitive price we pay.

The problem today is not that we multitask. We’ve always multitasked. The problem is that we’re always in multitasking mode. The natural busyness of our lives is being amplified by the networked gadgets that constantly send us messages and alerts, bombard us with other bits of important and trivial information, and generally interrupt the train of our thought. The data barrage never lets up. As a result, we devote ever less time to the calmer, more attentive modes of thinking that have always given richness to our intellectual lives and our culture—the modes of thinking that involve concentration, contemplation, reflection, introspection. The less we practice these habits of mind, the more we risk losing them altogether.

There’s evidence that, as Howard Rheingold suggests, we can train ourselves to be better multitaskers, to shift our attention even more swiftly and fluidly among contending chores and stimuli. And that will surely help us navigate the fast-moving stream of modern life. But improving our ability to multitask, neuroscience tells us in no uncertain terms, will never return to us the depth of understanding that comes with attentive, single-minded thought. You can improve your agility at multitasking, but you will never be able to multitask and engage in deep thought at the same time.